Pentazaindene stabilizers for photo-graphic emulsions sensitized with alkylene oxide polymers



- sosensitized. .aoth o jeq w ps p t thin United States Patent i PENTAZAINDENE STABILIZERS FOR PHOTO- 1 GRAPHIC EMULSIONS SENSITIZED WITH KYL E X E QL MERS Burt H. Carroll, RochestemN. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application April29, 1954, Serial No. 426,543

20 Claims. (Cl. 95-7) bilizers for photographic emulsions audio photographic.

tend to, lose sensitivity and to :become spontaneously developable without exposuretolight. There :is normally a detectable amount of the silver salt reduced duringdevelopment in the areas where noexposure was. given; this is commonly called ffogf and sometimes called fchemical Where-it is necessary to distinguish .betweenit and the eifects of accidental exposure to radiation;lin,, this.in- .vention,:'I am notconcerned with, the latter.

:Fog depends both on theemulsionand vthec'onditions of development; for a given emulsion it increaseswiththe degree of development. ditions, it tends .to increase with itime, temper,ature and rel- .ative humidity .of storage conditions;..it is commonpracv tice tomake acceleratedtests ofthe stability.of;photographicemulsionsbystorage at .increased temperature or .humidity,. or. both. It is, of course, desirable to.have

emulsions as stable as possible under the conditionsofhigh temperature and humidity Q which may occur in tropical climates, for example. Fog usually appears .over the whole area of the sensitive coating,.but whenv severe,.it frequently is non-uniform. -Fog.may alsobecausedby exposure to "chemicals, for example,v hydrogen sulfide and other reactive sulfur compounds, hydrogenperoxide vapor, and strongly reducing materials. 'While antifoggan'ts and stabilizers may-protect, tofsome.extent,;against suehseffects, it is normally understood that an antifoggant.pro- 1 tects against spontaneous growth'of fog'duringprolonged storage or storage at high temperatures and humiditi'es, Orduring development to maximum contrast and speed, or both.

Itisknown that the effectivesensitivity of photographic silver halide emulsions may be increased by addingto them-derivatives of alkylene oxidessuchv as ethylene oxide polymers having molecular weights of-300 orimore. ,The practical value of these compounds .iszseverelylimited by theirtendency to increase fog on storage .of rthephotographic film, especially storage at elevated, temperatures and humidities. It has been found diflicult, to control this by the antifoggants commonly.availablewithoutiusing quantities of antifoggant. which partlyneutralize the speed increase obtained from the alkyleneoxide derivatives. I 'Itistherefore an objectof thepresent inventionto provide a method for stabilizing photographicemulsions sensitizedwith alkylene oxide derivatives such as polyethylene oxides. A further object is to provide ameansfor reducing the fog produced upon keepingof emulsions so sensitized, especially emulsionsstored undertropicalor other adverse conditions. ,A. still further object is I to provide a means for stabilizing ,the speed and contrast of emuls ons ing description of my invention.

With constantdevelopment coni ice These objects are accomplished in general by adding to the emulsionsensitizedwith alkylene oxide polymers, one or more 7-sub'stituted 1,2,3,4,61pentazaindenes as stabilizing and fog inhibiting agents.

The alkylene oxide polymers used to sensitize the emulsions may be bf'vaiioiis' types. Tli e alkyliioxides from which the polymers are derived contain from 2 to 4 carbon atoms, e. g., ethylene oxide, propylene oxide and butylbiie oxide. The preparation of polymers from these compounds is described in,;Ellis, {The Chemistry of Synthetic Resins (1935), pages 990 ,to 994. These compounds are also referred to as 'polyalklyene glycols and their use as sensitizers for silver' halide emulsions is described in U. S. Patents 2,423,549 and'2,441,389.

nsderivatixesc slk eneoxi c .rnaval be used to sensitize the silver halide emulsions, e. g., condensation products of alkylene oxide with glycols, such as those having from 8 to 18 carbon atoms as described in U. S. Patent 2,240,472 and British Pater'if'443,559, as well as condensation products of alkylene oxides with aliphatic alcohols, aliphatic acids andaliphatic amines, and with phenols, that is, polyalkyleneethers, esters and amides, the preparation of which is described i n U'. S.,.Paterit 1,970,578, and condensation products ofalkylene oxides with hexitol ring dehydration products," "as described in U. S. Patent 2,400,532.

In each case the polyalkylene oxide or derivative of alkylene oxide should have a molecular weight of at least 300 and preferably a molecularweight of 1500 to 4000 or more.

The pentazaindenestabilizing agents which I propose to use have the followingstruc tiire:

in which X is hydrogen or an aryl radical, e. g., phenyl, prsulfophenyl, ior .pecarboxyphenyl, .Y is hydrogen; an amino radical, a hydroxy radical, an alkylradical, e. g., methyl, or a carboxymethylmercapto radical, and Z is an amino or hydroxyl radical.

Specific examples of compounds useful according to my invention are as follows:

. i t s. I

5 w1P divi rs-1 2 3,Marmar gen fi-hydroxy-T-a'mino-1,2,3,4,6-pentazaindene 5-methy1-7-hydroxy-1,2,3,4,6-pentazaindene 5-amino-7-amino-1,2,3,4,G-peutazaindene 7-hydroxy-1,2,3,4,6-pentazaiudene S-earboxymethylmercapto-T-atnino l,2,3,4,6-pentazaindene g N C 80111 was Q 2- p-sulfophenyl) -5-amino-7liydroxy-1,2,3,4,6 pentazain dene The principal purpose of my invention is to provide a means for maintaining the sensitivity and fog of silver halide emulsions at or close to initial optimum values under conditions of high temperature or humidity or both. Preferably the fog inhibitors which I propose to use are added to the emulsion at any stage during the process of manufacture prior to coating the emulsion. The pentazaindene fog inhibitor may be added to the emulsion in solution in any convenient solvent not injurious to the emulsion such as lower alcohols or ketones.

A solution of the pentazaindene which I employ when added in suitable concentration before coating to unsensitized or optically sensitized silver halide emulsions usually does not appreciably affect the sensitivity and fog when measurements are made soon after coating. 1

However, when sensitometric measurements are made (Lowe and Jones U.

after appreciable intervals of time under tropical or dry conditions of storage at elevated temperatures, these compounds do stabilize speed and maintain fog at a low level.

The alkylene oxide derivatives used to sensitize the emulsions may be illustrated by the following specific examples, although my invention is in no way limited to the use of these specific compounds.

HOCHzCHzO (CH2CH2O nCH2CH2OH Polyethylene oxide Di-(polyethylene-glycoxy) -decane HOCH2CH2O(CH2CH2O)11CH2CH2OC17H33 Polyethylene oxide oleyl other where n=an integer greater than about 10.

The preparation of silver halide emulsions involves three separate operations: (1) the emulsification and digestion or ripening of the silver halide, (2) the freeing of the emulsion from aqueous soluble salts usually by washing, (3) the second digestion or after-ripening to obtain increased sensitivity (Mees, The Theory of the Photographic Process, 1942, page 3). The fog inhibiting agents may be added at any stage, preferably after the final digestion.

The photographic emulsions which I use are of the developing-out type and best results have been obtained with gelatino-silver bromoiodide emulsions. However, emulsions of varying halide content may be used.

The emulsions may be chemically sensitized by any of theaccepted procedures, in addition to or in combination with the sensitizing with alkylene oxide polymers. The emulsions may be digested with naturally active gelatin, or sulfur compounds may be added such as those described in Sheppard U. S. Patent 1,574,944 and U. S. 1,623,499, and Sheppard and Brigham U. S. Patent 2,410,689.

The emulsions may also be treated with salts of the noble metals such as ruthenium, rhodium, palladium, iridium and platinum, all of which belong to group VIII of the periodic table of elements and have an atomic weight greater than 100. Representative compounds are ammonium chloropalladate, potassium chloroplatinate and sodium chloropalladite, which are used for sensitizing in amounts below that which produces any substantial fog inhibition, as described in Smith and Trivelli U. S. Patent 2,448,060, and as anti-foggants in higher amounts, as described in Trivelli and Smith U. S. Patents 2,566,245 and 2,566,263.

The emulsions may also be chemically sensitized with gold salts as described in Waller and Dodd U. S. Patent 2,399,083, or stabilized with gold salts as described in Damschroder U. S. Patent 2,597,856 and Yutzy and Leermakers U. S. Patent 2,597,915. Suitable compounds are potassium chloroaurite, potassium aurithiocyanate, potas' sium chloroaurate, auric trichloride and Z-aurosulfobenzothiazole methochloride.

The emulsions may also be chemically sensitized with reducing agents such as stannous salts (Carroll U. S. Patent 2,487,850), polyamines such as diethylene triaminc S. Patent 2,518,698), polyamines such as spermine (Lowe and Allen U. S. Patent 2,521,925), or bis-(fi-aminoethyl) sulfide and its watersoluble salts (Lowe and Jones U. S. Patent 2,521,926).

The emulsions may also be stabilized with the mercury compounds of Allen, Byers and Murray U. S. application Serial No. 319,611, Carroll and Murray U. S. application Serial No. 319,612 and Leubner and Murray U. S. application Serial No. 319,613, all filed November 8, 1952.

, pentazaindene.

The sensitizing and stabi lizing combinations -01. .polyalkylene oxides and pentazaindenes are efiective fiinflthv presence or absence of optical sensitizing dyes. Since optical sensitizing, may affect stability of emulsions with respect to sensitivity, fog and latent image changes, -the -posed-on-an-Eastman-type-lb Sensitometer anddeveloped gfOI' 5 minutes at6,8 F. in a developer of the following formula:

. Grams N-methyl-p=aminophenol sulfate 2.5 tHydroquinone 2:5 vsodium sulfite (desiccated) ,Sodium metaborate 10 ,Rotassium bromide .5

aWater-to 1 liter.

The films with and without the various addenda-were =.held,at 120 ,F. and constant humidity for 2 weeks and were then texposed and developed as indicated. "The results of tests for speed, .gamma and fogbefore'and after incubation of each of the samples were as-follows, speed being measuredas 10/1:

.without serious; desensitization. Qptimumiconcentrations ,-are'-:about. 0'.2to 1.0;gramiofi the pentazaindene-per gram mole of silver halide. These ;amounts :maygbmusedin combination with onesorzmorezofxttheechemicaltsensitizing and-stabilizingagents-listed above.-

F. and constant humidity unless othenwisetstated=..inithe eexaznples. Themesults ofeagingetestsrarectabulated below and -.:compare' .speed, gamma rand ting. of the vaemulsions One glitergof =ahigh speedgelatinwsilver bromoiodide Agent Fresh: Test Alter Incubation Qompound H. ,g. Speed Gamma Fog Speed Gamma Fog.

Control 2,300 0.92 0.07 s40 0. .74 5-A1nino-7-hydzoxy-1,2,8,4,6-

..nentazainde ne..(l) .60. 2,100 0.89 12 1,780 0.70 20 Oleyl alcohol-ethylene oxide .45 a, 700 0. 7s .09 000 0. 03 2% },3,s00 0.72 .18 2,250 0. 00 .24

. likelydo tolerateuassmuchias :this upper limit Example 2 Oneliterof a negative speed gelatino-silver bromo- 13 The stabilizing action :svasndeterminedi hy incubation .of the emulsions usually :for zone mrirtwo'twecks at 120 iodide emulsion-was chemically sensitized with sulfur and gold compounds as in Example 1 and was panchromatically sensitized. 'Toa portion of the emulsion there was added-'0J7-gram' per gram mole of silver halide of the condensation product of oleyl alcohol with ethylene oxide nsed'in'Exan-iple land to other portions of the emulsion there were added 0.7 gram per gram mole of silver halide o' f the oleyl alcohol-ethylene oxide condensation product "and --varying amounts of 5-amino-7-hydroxy-1,2,3,4,6- --pentazaindene.

The'emulsions-were coated on film base and were ex- ;posed-and-developed-as in-Example '1. "The-films with and withoutthe-various addenda wereheldat 120 F. and constant humidity for one week and were then exaposedz-and-developed as in'Example 1, speed being-read in Sheppard U. S. Patent 1,574,944 and potassium chloroaurate and optically sensitized with 1,1'-diethyl-2;2"- cyanine iodide. To a portion of the emulsion. ,therez was added 0.45 gram per gram mole of silver halide of the condensation product of oleyl alcohol with approximately 15 moles of ethylene oxide, and to another portion of the emulsion there was added 0.60 gram per gram mole of silver halide of S-amino-7-hydroxy=l,2,3.;4,6-

Portions tot the temulsions. containing the addenda0weresalsormixcd.tonobtainQua-emulsion. 0ntainingboth .the ..oleyl. alcohol-ethytlene noxidencondensa- 1.tionproduct.and.the;pentazaindene. f

:The; emulsions werecoated on tilm baseeandswvere .c

.emul'sion containing 0224' mole 'o'fi silver halide per*-'=liter .as'/E:

Agent Fresh Test After Incubation Compound H9512 WWW.

,g. Speed Gamma Fog Speed Gamma Fog Qley alcalioliethylen oxide I-condensationgproduct;(I) 12,800 0.90 0.21 12, 500 0.79 0.28,

}13, 700 0.93 .21 12, 00 0. .27 }14;700 0.99 0.22 13,100 0.19 0.29 5 }12,s00 1.00 .16 14,700 0. 5 :16 -g }10,s00 0.95 .17 14,400 0.79 .18

was digested with a sulfur compound such as disclosed Example 3 One liter-of a negativerspeed gelatino-silver brornoiodide emulsion was chemically sensitized withsulfurgand gold, compounds as -in--Exampl e 1 and waspanchromatica'lly sensitized. To portions-of. this emulsionthere were added, the amounts indicated in the table of the condensa- ,tion;product, of oleylfaleohol with ethylene Oxide used inExample 1 and the amounts of the pentazaindenes also indicated.

zitheaemulsionsiwerecoated. on film base andwere exaposed and developed v,as-in-, l3xamp1e 1. The films .were athen incubated-as in Example 2 .and both incubated and :unincubated. samples were .exposed and developed asiin fixamplei'la speed being readas 1.0/1:

Agent Fresh Test After Incubation Compound per mole g Speed Gamma Fog Speed Gamma Fog Control 2, 900 1.06 1,700 83 27 Polyethylene oxide oleyl I ether (I). .4? 5, 200 87 14 3, 000 69 35 4 5, 7 Dmydr 60 5, 400 .88 .19 4, 300 69 22 Control. 3, 000 l. 05 12 2,000 80 55 I 25 4, 300 9G l3 1, 600 67 68 5 S-Met'nylJ-hydroxypentaza- 4, 400 98 12 3, 500 .82 .28

indene 90 2,200 .72 .11 1,140 .57 .16 3,600 .72 .11 2,750 .63 .16 }3,950 .00 .10 3,000 .73 .17 2, 350 78 ll 1,060 67 24 4, 450 .74 13 1, S 60 28 I Z-(p-Sulfophenyl)--amino-7- }14, 700 95 B, 250 73 36 pentazaindene 1. 0

Example 4 the general formula is aryl) While I believe that the Grams N-methyl-p-aminophenol sulfate 1.5 Hydroquinone 1.3 Sodium sulfite (desiccated) 75 Borax 4.5 Potassium bromide 0.4

Water to 1 liter Portions of the films with and without the addenda were incubated as in Example 2, and were then exposed and developed as in the case of the fresh samples. The results were as follows:

compounds which I use have the general formula expressed above, I include within the scope of my invention any isomeric or tautomeric forms of the compounds which may result fromtheir preparation in the manner described and which are effective fog inhibiting or stabilizing agents for photographic emulsions.

The polyethylene oxide lauric ester of Example 4 was made by condensing 1 mole of lauric acid with approximately 26 moles of ethylene oxide.

The polyethylene .oxide phenol ether of Example 4 was prepared as follows:

In a S-necked, 500-1111. flask was placed 14.1 grams (0.150 mole) of redistilled phenol and 14.1 grams of dry benzene. The system was swept out with dry nitrogen. Five drops of boron-trifiuoride-ethyl ether complex was added, and the flask placed in a C. water bath.

Ethylene oxide was added slowly over a period of 4 days beneath the surface of the alcohol through a gas addition tube until a gain in weight of 277 grams was observed. An internal temperature of 50-60 was maintained and additional small amounts of catalyst (up to a total of Agent Fresh Test Alter Incubation Compound per mole g Speed Gamma For; Speed Gamma Fog Control 2, 700 68 .10 1,470 56 14 Polyethylene oxide laurie I ester 4, 350 68 10 2, 500 19 a riie'tii 'i-i h'iibky ijfiT 4, 550 .78 .10 2,150 1. 0 .14

4,6-pentazaindene (II) .95.... Polyethylene oxide phonyl ether (III) 1.0. 3, 800 67 10 2, 250 55 .17 m 4,050 .74 .11 1,900 .00 .13

3, 500 67 .10 2,000 57 17 H }3.500 .68 .10 2,000 .54 .13 Polyethylene oxide gll monolaurate other (V) 3, 500 68 .09 2, 250 55 l4 3,300 .12 .00 2,300 .55 .11

amide (VI) 3, 800 .70 10 l, 690 57 20 4,250 .15 .00 2, 250 .53 .13

The pentazaindenes of my invention may be prepared in the manner described in English, Vaughan and Roblin U. S. Patent 2,407,204, September 3, 1946 (where X in the general formula is hydrogen) or Parker and Webb U. S. Patent 2,543,333, February 27, 1951 (where X in 20 drops for the entire reaction) were added as needed to maintain optimum absorption of ethylene oxide.

Ninety-six percent of the reaction mixture was transferred to a 500-ml. flask, and evacuated to constant weight in the-50 oath, using a Hi-Vac pump at 1-2 mm. The

yield of productwvas ISS-grams. 'I-he 'mola'r ration of phenolto ethylene oxide 'unitsqwaslto 2823. I

"'Ihe'pc'vlyet'hylene oxide-glycine compound of Example 4 was prepared as follows:

(0.2 mole) of ethylene oxide,"and"0.-'15;gr am of; sodium acetate was heated-in a sealed ,-tube-'at"l35-'C. for 16 hours. *The; product was dissolved in benzene, treated with a ctivate'd charcoahi'filter'ed, and the-solventremoved .in vacuo. "The yield 'of'dark brown,tacky, semi-solid was f6;4 grams(98% J 1he ,polyethylene 'oxide-laurylamide compound of'llxample 4swas prepared as;follows:

A'mixture. of2 grams.(0.'0l mole) (of lauramide, 8.8

grams ,(0.2 mole) .of ethylene oxide and 0.2 gram of 3.6 grams (0.01 mole) of glucose monolaurate, 8-.'8

grams (0.2 mole) of ethylene oxide, and 0.4.gram of so dium carbonate were heated in a sealed tube at 170 to 180 C. for hours. The mixture was dissolved in benrzene and-stirred with 3 grams of.v sodium carbonate=and Stgrams-ofxDaIcO. The solution-was:filtered;.and the tsolvent removed; the product iwas a dark, amber-colored :liquid. 'Theyield was 11 grams.

:The. polyethylene oxide polymers .usedrin the emulsions raccording tow my invention may -be zprepared either .-by

polymerizing ethylene oxide in the presence of aliphatic acids, aliphatic amines or phenols, or by reacting the polymerized polyethylene oxide with aliphatic acids, acid chlorides, or esters, which produces similar products.

Instead of incorporation in the silver halide emulsion the fog-inhibitors of my invention may be incorporated in a colloid layer such as a gelatin layer in contact with the emulsion.

The fog-inhibiting agents which I have described may be used in various kinds of photographic emulsions. In addition to being useful in non-sensitized emulsions they may also be used in orthochromatic, panchromatic and X-ray emulsions. If used with sensitizing dyes, they may be added to the emulsion before or after the dyes are added. Various silver salts may be used as the sensitive salt, such as silver bromide, silver iodide, silver chloride or mixed silver halides. The azaindene compounds and alkylene oxide polymers may be used in emulsions intended for color photography, for example, emulsions containing color-forming couplers, or emulsions to be developed by solutions containing couplers.

The dispersing agents may be gelatin or other colloid such as collodion, albumen, cellulose derivatives or synthetic resins.

It will be understood that I contemplate as included within my invention all modifications and equivalents falling within the scope of the appended claims.

I claim:

1. A light-sensitive silver halide emulsion sensitized with an alkylene oxide polymer selected from the class consisting of (1) polyalkylene glycols, (2) condensation products of alkylene oxide with glycols, (3) condensation products of alkylene oxide with aliphatic compound-s selected from the class consisting of alcohols, acids and amines, (4) condensation products of alkylene oxide with phenols, and (5) condensation products of alkylene oxide with hexitol ring dehydration products, said alkylene 0xide containing from 2 to 4 carbon atoms and said alkylene oxide polymer having a molecular weight of at least 300, said emulsion containing as a fog inhibiting agent a pentazaindene having the formula:

"in whichX is selected from the class consistingof hydrogenand aryl.radicals,' Y is selectedfrom' the class consisting of hydrogen, amino. radicals, hydroxy radicals, al-

kyl radicals, and carboxymethylmercapto radicals, and Z is selected fromthe class consisting otamino. radicalsand Ihydroxy radicals.

with hexitol; ring dehydration products, ;said alkylene o x idecontainingtrom 2 to '4-carbonatoms; and said alkylene oxide polymer having a molecular-weight of, at least 300, said emulsion containing. as *a'ifog inhibiting agent ,5.-

"aminoi7=hydroxy 1,2,3,4,6-pentazaindene. v "3. A "lightisensitive silver "halide emulsion sensitized Wuhan-ethylene oxidegpolymer-having a molecular Weight of at" least 300, "said emulsion containing as a fog inhibiting agent a 7-hydroxy-l,2,3,4,6-pentazaindene.

"4. Alight-sensitive silver halide emulsion sensitized with a condensation product of ethylene'oxidewith an'aliphatic alcohol, said condensation product" having a molecular Weight-of at least- 300, said-emulsion containing as a fog inhibiting agent a 7-hydroxy-'1,2;3;4 ,6-pentazaindene.

5. A light-sensitive silver *halide'emulsion sensitized with a condensation product of ethylene oxide with an aliphatic acid, said condensation product having a molecular weight of at least 300, said emulsion containing as a fog inhibiting agent a 7-hydroxy-l,2,3,4,6-pentazaindene.

6. A light-sensitive silver halide emulsion sensitized with a condensation product of ethylene oxide with an aliphatic amine, said condensation product having a molecular weight of at least 300, said emulsion containing as a fog inhibiting agent a 7-hydroxy-l,2,3,4,6-pentazaindene.

7. A light-sensitive silver halide emulsion sensitized with an ethylene oxide polymer having a molecular weight of at least 300, said emulsion containing as a fog inhibiting agent 5-methyl-7-hydroxy-l,2,3,4,6-pentazaindene.

8. A light-sensitive silver halide emulsion sensitized with a condensation product of one mole of oleyl alcohol with approximately '15 moles of ethylene oxide, said emulsion containing as a fog inhibiting agent S-methyl- 7-hydroxy-1,2,3,4,6-pentazaindenc.

9. A light-sensitive sulfur-sensitized silver halide emulsion additionally sensitized with an alkylene oxide polymer selected from the class consisting of (1) polyalkylene glycols, (2) condensation products of alkylene oxide with glycols, (3) condensation products of alkylene oxide with aliphatic compounds selected from the class consisting of alcohols, acids and amines, (4) condensation products of alkylene oxide with phenols and (5) condensation products of alkylene oxide with hexitol ring dehydration products, said alkylene oxide containing from 2 to 4 carbon atoms and said alkylene oxide polymer having a molecular weight of at least 300, said emulsion containing as a fog inhibiting agent a pen'tazaindene having the formula:

z t N 11 in which X is selected from the class consisting of hydrogen and aryl radicals, Y is selected from the class consisting of hydrogen, amino radicals, hydroxy radicals, alkyl radicals, and carboxymethylmercapto radicals, and Z is selected from the class consisting of amino radicals and hydroxy radicals.

10. A light-sensitive sulfur-sensitized silver halide emulsion additionally sensitized with an ethylene oxide polymer having a molecular weight of at least 300, said emulsion containing as a fog inhibiting agent -methyl-7-hydroxy-l,2,3,4,6pentazaindene.

11. A light-sensitive sulfur-sensitized silver halide emulsion additionally sensitized with a condensation product of one mole of oleyl alcoholwith approximately moles of ethylene oxide, said emulsion containing as a fog inhibiting agent 5-methyl-7-hydroxy-1,2,3,4,6-pcntazaindene.

12. A light-sensitive sulfur-sensitized silver halide emulsion additionally sensitized with a condensation product of ethylene oxide with an aliphatic alcohol, said condensation product having a molecular weight of at least 300, said emulsion containing as a fog inhibiting agent a 7-hydroxy-1 ,2,3,4,6-pentazaindcne.

13. A light-sensitive sulfur-sensitized silver halide emulsion additionally sensitized with a condensation product of ethylene oxide with an aliphatic acid, said condensation product having a molecular weight of at least 300, said emulsion containing as a fog inhibiting agent a 7-hydroxyl,2,3,4,6-pentazaindene.

14. A light-sensitive sulfur-sensitized silver halide emulsion additionally sensitized with a condensation product of ethylene oxide with an aliphatic amine, said condensation product having a molecular weight of at least 300, said emulsion containing as a fog inhibiting agent a 7-hydroxy-l,2,3,4,6-pentazaindene.

15. The emulsion of claim 9 which is additionally chemically sensitized with gold salts.

16. The emulsion of claim 10 which is additionally chemically sensitized with gold salts.

17. The emulsion of claim 10 which is additionally stabilized with mercury salts.

18. The emulsion of claim 10 which is additionally chemically sensitized with gold salts and stabilized with a salt of the general formula selected from the group consisting of RzMXs, R2MX4 and R3M"Xs, where R is selected from the group consisting of hydrogen, an alkali metal and ammonium, M is a metal selected from the group consisting of platinum, palladium, iridium, rhodium and ruthenium, M is a metal selected from the group consisting of platinum and palladium, and M" is a metal selected from the group consisting of iridium and rhodium, and X is a halogen atom.

19. The emulsion of claim 10 which is additionally chamically sensitized with gold salts and stabilized with a palladium salt having the structure RzPdCls where R is selected from the group consisting of alkali metal and ammonium.

20. The emulsion of claim 10 which is additionally chemically sensitized with gold salts and stabilized with mercury salts.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A LIGHT-SENSITIVE SILVER HALIDE EMULSION SENSITIZED WITH AN ALKYLENE OXIDE POLYMER SELECTED FROM THE CLASS CONSISTING OF (1) POLYALKYLENE GLYCOLS, (2) CONDENSATION PRODUCTS OF ALKYLENE OXIDE WITH GLYCOLS, (3) CONDENSATION PRODUCTS OF ALKYLENE OXIDE WITH ALIPHATIC COMPOUNDS SELECTED FROM THE CLASS CONSISTING OF ALCOHOLS, ACIDS AND AMINES, (4) CONDENSATION PRODUCTS OF ALKYLENE OXIDE WITH PHENOLS AND (5) CONDENSATION PRODUCTS, SAID ALKYLENE OXIDE WITH HEXITOL RING DEHYDRATION PRODUCTS, SAID ALKYLENE OXIDE CONTAINING FROM 2 TO 4 CARBON ATOMS AND SAID ALKYLENE OXIDE POLYMER HAVING A MOLECULAR WEIGHT OF AT LEAST 300, SAID EMULSION CONTAINING AS A FOG INHIBITING AGENT A PENTAZAINDENE HAVING THE FORMULA: 